Aastra Telecom IP Phone - Manual (Page 168)

160 Model 57i IP Phone User Guide
Additional Features
1. Click on Basic Settings->Preferences.
2. Go to the "General" section .
3. Enable the "Suppress DTMF Playback" field by checking the check box. (Dis-
able this field by unchecking the box). Default is disabled.
4. Click to save your settings.